A problem has recently arisen that, in magnetic disk devices mounted in mobile appliances such as notebook computers, it is necessary to make a cover sufficiently rigid in the direction toward the magnetic disk surface. For example, in notebook computers and magnetic disk devices incorporated in the notebook computers, the magnetic disk device is ordinarily mounted under a palmrest portion closer to the computer front side relative to the keyboard. In such a case, if the palmrest portion is strongly pressed by a person, the pressed portion is warped and presses the cover of the magnetic disk device mounted under the palmrest portion incorporated mounted. The cover of the magnetic disk device is ordinarily made a thin metal plate. At worst, a portion of the warped cover is brought into contact with the magnetic disk rotating in the magnetic disk device. There is a demand for thinner mobile appliances and thinner magnetic disk devices incorporated in the mobile appliances. Therefore, it is thought that this problem will become more serious.
In view of this problem, devices for improving the rigidity of covers have been provided. For example, a method is known in which a reinforcing member of a high rigidity is placed in a space between a magnetic disk and a cover and is connected to the cover and to a base by using fastening screws (see, for example, Japanese Patent Laid-Open No. 2002-343071).
The shape of a conventional cover will be described with reference to FIGS. 6 to 8. FIG. 6 shows a magnetic disk device using a conventional cover. FIG. 7 is a sectional view of the conventional cover. FIG. 8 is a sectional view taken along a line passing through the rotating shaft of a motor. As can be seen in FIG. 7, drawn portions 70 having a semicircular sectional shape are formed in a sectoral pattern above and opposite a magnetic disk to ensure the desired rigidity of the cover.